What is Juvenile Myoclonic Epilepsy?
Juvenile myoclonic epilepsy (JME), also known as Janz syndrome or impulsive petit mal, is a type of epilepsy that is inherited and affects the whole brain. The term “idiopathic” means its causes are unknown. This condition was first written about by a doctor named Herpin in 1867, and then later referred to as “impulsive petit mal” by doctors Janz and Christian in 1957, and as JME by Lund in 1975. The main features of this condition are a specific type of seizures known as absence, myoclonic, and generalized tonic-clonic seizures.
“Absence” seizures are brief and consist of sudden lapses of consciousness. “Myoclonic” seizures result in involuntary muscle twitching or jerking. “Generalized tonic-clonic” seizures, often known as grand mal seizures, involve a loss of consciousness and violent muscle contractions. So, if someone has JME, they would experience one or more of these types of seizures.
What Causes Juvenile Myoclonic Epilepsy?
Juvenile Myoclonic Epilepsy (JME) is a condition that is both idiopathic, meaning its cause is unknown, and hereditary, meaning it can run in families. Interestingly, about half of the people who have JME also have a family member with the same condition.
Risk Factors and Frequency for Juvenile Myoclonic Epilepsy
Juvenile Myoclonic Epilepsy (JME) is a common type of epilepsy that often begins in childhood or adolescence. It accounts for about 5% to 10% of all epilepsy cases.
- JME affects both males and females equally, although some studies suggest more females might be affected.
- The typical age for JME to start is between 12 and 18 years old.
Signs and Symptoms of Juvenile Myoclonic Epilepsy
Juvenile myoclonic epilepsy (JME) is a condition that typically begins in adolescence, with most people experiencing their first seizures between ages 12 and 18. However, it can start as early as age 5 or as late as 34. There are three main types of seizures associated with JME: myoclonic, generalized tonic-clonic (GTC), and absence seizures.
- Myoclonic seizures: These are brief, usually affect both arms, and sometimes the legs alongside preserving consciousness. These seizures are the key characteristic of JME and necessary for a diagnosis. Misdiagnosis can occur, as these may seem like simple twitches or signs of anxiety. Often, these seizures become stronger and more frequent, leading to GTC seizures a few months later.
- GTC seizures: These are experienced by 85%-90% of JME patients.
- Absence seizures: These happen in 20-40% of JME patients and often manifest first, generally 3 to 5 years before other seizures. These can begin as early as age 5 or 6, and due to their early appearance, they are sometimes misdiagnosed as childhood or juvenile absence epilepsy.
Most often, seizures with JME happen about half to one hour after waking up in the morning, especially the myoclonic seizures. Common triggers of these seizures include lack of sleep, drinking alcohol, emotional stress, anxiety, and fatigue. A significant percentage of JME patients (around 30%-40%) are photosensitive, meaning seizures can be triggered by flashing lights, sunlight, TV, and computer screens. These photosensitive patients usually begin experiencing seizures earlier. Regardless of these symptoms, physical examinations usually appear normal, and cognitive abilities are well preserved. However, JME patients may have a higher chance of experiencing psychiatric conditions like anxiety, mood disorders, and personality disorders.
Testing for Juvenile Myoclonic Epilepsy
Diagnosing Juvenile Myoclonic Epilepsy (JME), a type of epilepsy common in teens, typically involves careful review of a patient’s medical history. A typical physical check-up might not give away much useful information for diagnosing this condition. However, an electroencephalogram (EEG), a test that measures electrical activity in the brain, is a very useful tool in confirming JME.
In most cases of JME, the EEG will show irregular patterns, especially when the patient is shifting between sleep and wakefulness. The common EEG reading for JME patients shows erratic spike-and-wave discharges, which are abnormal brain waves, in the front-central part of the brain. The EEG additionally could indicate the occurrence of myoclonic jerks, which are involuntary muscle movements – a key symptom of JME. Some patients also show specific EEG patterns during certain kinds of seizures, such as generalized tonic-clonic (GTC) seizures, which cause a loss of consciousness and violent muscle contractions, and absence seizures, which cause short losses of consciousness. Photoc stimulation, a process where the patient is subjected to varying levels of light, can further enhance the EEG results, as JME is known to be sensitive to light.
Even though an electroencephalogram (EEG) provides strong evidence for a JME diagnosis, sometimes more advanced imaging techniques like Magnetic Resonance Imaging (MRI), Magnetic Resonance Spectroscopy (MRS) and Positron Emission Tomography (PET) are used to look for structural abnormalities in the brain of JME patients, which might be missed in regular imaging.
Treatment Options for Juvenile Myoclonic Epilepsy
Most people with JME, or Juvenile Myoclonic Epilepsy, respond positively to anti-epilepsy drugs. The most effective medication for treating all types of seizures associated with JME is Valproic acid. However, it does need to be used with caution in women who could become pregnant, due to side effects that could harm a developing baby.
Other drugs that can be used to treat JME include levetiracetam, lamotrigine, topiramate, and zonisamide. Keep in mind that lamotrigine may increase the frequency of a certain type of seizure called myoclonic seizures, but it is still often used to treat JME because it helps control other types of seizures.
If a person with JME only has a certain type of seizure called absence seizures, another medicine called ethosuximide might be used. Clonazepam can help control myoclonic jerks, a common symptom of JME.
Some medications are not recommended for treating JME because they may increase the frequency of certain types of seizures. These include carbamazepine, oxcarbazepine, and phenytoin. The same caution applies to certain other medications, including vigabatrin, tiagabine, gabapentin, pregabalin, and primidone.
Very few people do not respond adequately to these medications, and in such cases, combination therapy or a procedure called vagus nerve stimulation might be considered. This involves electrical stimulation of a nerve in the neck to help control seizures.
What else can Juvenile Myoclonic Epilepsy be?
When trying to diagnose Juvenile Myoclonic Epilepsy (JME), doctors might encounter other epilepsy syndromes that display similar symptoms, particularly at different stages of their development. These might include:
- Childhood or juvenile absence epilepsy
- Eyelid myoclonia with absences
- Progressive myoclonic epilepsy
- Photosensitive occipital epilepsy
- Epilepsy with grand mal seizures upon awakening
- Hypnogogic myoclonus (also known as a “hypnic jerk”)
- Non-epileptic seizures
It’s crucial for these conditions to be carefully considered and differentiated from JME to ensure the most accurate diagnosis and appropriate treatment.
What to expect with Juvenile Myoclonic Epilepsy
Seizures in most patients with Juvenile Myoclonic Epilepsy (JME) tend to be well managed with medication and often get better after a person reaches their 40s. However, no matter how long a period the patient spends without seizures, they will need to continue treatment throughout their life. This is because if they stop taking their medication, the risk of having more seizures is high.